Lately, Facebook is archiving all of the chat conversations under Messages. I have been unable to find out an option to disable it. It even shows up conversations that happened 2-3 years back. If anyone is aware of how can it be disabled, please share.
I haven't installed any 3rd party or Facebook application. A lot of my other friends are also facing the exact same issue. Probably, it's some kind of bug that has not got fixed as yet.